1. Field of the Invention
The present invention relates to a ridercontrolled working vehicle such as a tractor for use in various fields such as agriculture, civil construction, and transportation, for example, and more particularly to a chassis frame for such a working vehicle.
This application is copending with related and commonly assigned U.S. patent applications U.S. Ser. No. 764,433 and U.S. Ser. No. 764,434, both filed Aug. 9, 1985. Note, however, that each of such applications is directed to novel subject matter which is patentably distinct from the novel subject matter of the present application.
2. Description of Relevant Art
Various conventional rider-controlled working vehicles are known. The known rider-controlled working vehicles have a chassis frame including an intermediate member such as a power transmission case with its front and rear surfaces coupled respectively to the rear surface of the casing of an engine unit located in a front portion of the vehicle and the front surface of a gear transmission case disposed in a rear portion of the vehicle. Such known, conventional vehicles are disclosed in Japanese Laid-Open Utility Model Publication Nos. 55-138124 published on Mar. 26, 1979, 57-143923 published on Sept. 9, 1982, 57-199131 published on Dec. 17, 1982, and 58-100130 published on July 7, 1983, for example. Where a differential is connected to front wheel axles of the known vehicles, it is disposed below a front frame member. Where a working vehicle has a power output shaft for a working unit to be coupled to the front end of the vehicle body, the power output shaft projects from the front frame member as disclosed in Japanese Laid-Open Publication No. 57-199131 or is exposed below the front frame member as disclosed in Japanese Laid-Open Publication Nos. 57-143923 and 58-100130.
There are many disadvantages associated with the chassis design as of the known rider-controlled working vehicles, some of which are as follows. The conventional chassis frame comprises a number of frame members joined together. If these frame members were to be coupled in planes perpendicular to the longitudinal axis of the vehicle, it would be difficult to maintain a uniform degree of mechanical strength of the chassis frame since the coupled areas would be subject to bending and twisting stresses imposed during movement of the vehicle. It would also be difficult to achieve a desired dimensional accuracy because many bolt holes would have to be formed and many bolts would have to be tightened, resulting in an increased number of assembling steps. In designs where the engine unit casing is part of the chassis frame, the engine vibration will be applied directly to the vehicle body. The working vehicle with the differential mechanism situated below the chassis frame has a reduced minimum height from ground and hence is not suitable for travel over rough terrain. If the height of the chassis frame were increased to eliminate such a drawback, then the height of the vehicle or the engine hood would also be increased, resulting in difficulty in handling and maneuvering the vehicle. Where the power output shaft is located on the front end of the vehicle and projects forwardly from the chassis frame or is exposed below the chassis frame, foreign objects tend to interfere with the power output shaft when it is not in use.
The present invention has been made in an effort to eliminate the aforesaid disadvantages of the conventional rider-controlled working vehicles.